Intra-clustering communication component for mod_cluster

Communication component that handles intra-cluster communication within the AS instances, aggregates information and passes to the component that communicates with mod_cluster on the httpd side.

Tracks cluster membership. A node (one per cluster) or set of nodes (one per domain) are determined to be master.

All nodes receive events from a listener layer indicating deployments, JBossWeb Server start and stop etc. Pass those one to their master via RPCs. All nodes also respond to periodic RPCs from master node asking for load information.

Master node(s) inform httpd side about events that are received. Periodically request load information from nodes, aggregate into overall load factors and provide to mod_cluster via STATUS messages. Inform mod_cluster about topology changes (crashed members, etc).

Initial expectation is this will be based upon HASingletonSupport class.